This invention relates to the field of clinical diagnostic testing and more particularly to novel reagents and methods for making biological assays on body fluids.
A large variety of test reagents and methods are available for use in determining the character of various body fluids to assist in the diagnosis of certain pathological conditions. Tests for determination of certain types of biological activity or the presence and quantity of certain biologically active components provide information indicating the presence or absence of disease or other physiological disorder. In accordance with such tests, the biological specimen to be analyzed, for example, a sample of a body fluid, is typically mixed with a liquid reagent formulation which contains a reagent capable of effecting a reaction which causes a measurable change in the specimen/reagent system. Very often the reaction which takes place in the test is an enzymatic reaction. Certain tests are designed, in fact, to determine the presence of a particular enzyme and in such cases the reagent formulation may contain a substrate upon which the enzyme to be determined is known to act. In other cases, the determination may be for a material which is known to be reactive substrate in an enzymatically catalyzed reaction. In either case, the reagent formulation very commonly contains an enzyme, a coenzyme or both. Because the catalytic activity of most enzymes is specific to a particular reaction, test reagents can be formulated which are effective to determine specific biological components or activities even in a complex body fluid containing a large number of other components which might interfere with efforts to obtain a purely chemical analysis. Moreover, many of the components which are to be determined have highly complex chemical structures which would render direct chemical analysis difficult even in the absence of any contaminants.
Unfortunately, enzymes and coenzymes are generally rather delicate materials which may be readily denatured by heating and which also tend to degenerate upon storage. Many of the substrate materials used in biological assay reagent formulations are similarly unstable. Liquid reagents containing such components are therefore not generally susceptible to storage and must be freshly prepared shortly prior to use in clinical diagnostic testing. Because of the relative expense of enzymes and coenzymes and the skill required to prepare a reagent formulation containing these materials which can be utilized to obtain accurate clinical diagnostic test results, the instability of the liquid formulations has motivated a substantial amount of research to develop reagents in a relatively storage-stable form. Much of this effort has been directed to the development of solid, dry, water-soluble formulations which can be dissolved in water at the time of testing to provide a fresh liquid reagent useful in the test. Typical prior art dry reagent formulations are disclosed in Deutsch U.S. Pat. No. 3,413,198 and Stern et al. U.S. Pat. No. 3,546,131.
A dry reagent formulation satisfactory for use in preparing liquid reagents for routine clinical diagnostic tests should satisfy a number of criteria. It must be readily soluble in a solvent compatible with the biological specimen, usually water. It should be capable of solubilizing proteinaceous material in the specimen. Moreover, it should be readily susceptible to packaging in convenient sized packages and be adapted for rapid dissolution in the solvent to provide a liquid reagent of proper strength for a given test or series of tests.